(1) Field of the Invention
This invention relates to a carburetor suitable for use with an internal combustion engine equipped with a turbosupercharger.
(2) Description of the Prior Art
An internal combustion engine equipped with a turbosupercharger having a turbine driven by exhaust gases by utilizing their energy to drive a compressor mounted in a suction passage to compress air drawn by suction before delivering it to a combustion chamber is capable of delivering air greater in volume by 30-40% than ordinary internal combustion engines.
In an internal combustion engine equipped with a turbosupercharger, the amount of oxygen in the air increases and the fuel-air mixture tends to become lean. This phenomenon has given rise to the problem that in an engine speed range in which the turbosupercharger is in action, the temperature of combustion might rise and knocking might occur, thereby causing deterioration of the drivability of an automotive vehicle and damaging the internal combustion engine.
A proposal has been made, in an internal combustion engine equipped with a turbosupercharger, to increase the volume of fuel injected through a fuel injection valve when the turbosupercharger is activated, as disclosed in Japanese Patent Laid-Open No. 28560/73, for example.
Besides the fuel injection system disclosed in the Japanese Patent Gazette noted hereinabove, a carburetor is also used as a fuel supply system for internal combustion engines. It is desired that similar measures be taken with respect to carburetors.
In the case of a carburetor, one only has to increase the diameter of a fuel jet of the carburetor to keep fuel-air mixtures from becoming lean. However, when this step is taken, fuel might be wasted or exhaust emissions might give rise to the problem of air pollution in an engine speed range in which supercharging does not take place. To obviate this problem, fuel should be increased in volume only when the turbosupercharger is put into action.
Meanwhile, a double supercharger including a primary carburetor and a secondary carburetor is becoming more popular than a single carburetor. This makes it necessary to control both the primary and secondary carburetors to increase the fuel flow when the turbosupercharger is activated. Particularly, the range of engine speeds in which the turbosupercharger is put into action matches the operation condition in which the primary and secondary carburetors are both actuated, so that it is necessary to control main fuel systems of the primary and secondary carburetors.